Radio apparatus



April 26, 1932.

R. r H. HAMMAN RADIO APPARATUS Filed Dec. 12, 1929 INVENTOR 23495644 /7f /%7/WMA/V AT NEY Patented Apr. 26, 1932 UNITED. STATES PATENT OFFICE RUSSELL H. HAMMAN, OF CHICAGO, ILLINOIS, AS$IGNOR TO GRIGSBY-GBUNOW COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OI ILLINOIS v RADIO APPARATUS This invention relates to radio-frequency transformers and particularly to the constructionthereof. In order that such transformers may be manufactured in large quantities, it is essential that they be simple in 7 structure and mechanically rigid so that the relation between the various parts will be the same at all times.

In my preferred form, the structure comprises two coilsof wire, each wound on a tube of insulating material. The two tubes are preferably of different cross-sectional dimensions so that one may fit within the other. A. plurality of eyelets or other fastening means join the two ends of the tubes together to form a rigid concentric structure. In order to maintain proper spacing, bushings may be disposed around each eyelet between opposing tube surfaces.

This structure is preferably provided with a metal base upon which only one of the coils is mounted at one end. Thus one tube completely supports the other. A metal cap engages the .base and covers the transformer,

.25 serving to shield it mechanically and electrically.

A balancing coil used in connection with the transformer as a neutralizing means may be made an integral part of the structure.

30 This balancing coil is preferably disposed within and at one end of one of the tubes with its axis perpendicular to the axis of the two coils. In order to maintain the balancing coil, which is likewise wound on a tube, it 35 is desirable to cut the ends of the tube at an acute angle to its axis to provide tongues which contact with the inner surface of one of the concentric tubes. The tongues may then be joined to one of the tubes to maintain the 4 balancing coil in proper position.

Referring to the drawings, Fig. l is a diagrammatic showing of a circuit with a transformer partly in section connected;

Fig. 2 is a plan view looking down upon 4 the transformer with part of the shield broken away;

Fig. 3 is a detail of the shield;

The circuit is well known and comprises an antenna 1 connected to inductances 2 and W 3. Inductance 2 is shunted by condenser and has its other end grounded. Inductance 3 is connected by wire 5 to grid 6 of a vacuum tube 8. A tuning condenser 9 is connected from wire 5 to ground. Anode 12 of tube 8 is connected by lead 13 to primary 14 of a radio frequency transformer 7. The other end of the primary is connected bylead 15 to a condenser 16 and battery 17, both of the latter being grounded. An equipotential cathode 20 of tube 8 is grounded through a suitable resistance 21, while heater filament 22 is connected by suitable leads 23 to a source of heating current.

Secondary coil 25 of the transformer 7 has one terminal connected by a lead 26 to the grid 28 of a vacuum tube 29. The other end of secondary 25 is connected by lead 30 to a balancing coil 31, whose axis is perpendicularto the axis of secondary 25. Coil 31 is grounded at its other end. A tuning condenser 33 is shunted across secondary 25 in the usual manner. In order to obtain complete neutralization, a condenser 35 is connected between grid 6 of tube 8 and the junction of secondary 25 and balancing coil 31.

The cathode 36 of tube 29 is connected to cathode 20, while filament 37 is connected by leads 38 in parallel to filament 22 of tube 8. Anode 40 of tube 29 feeds into a similar transformer 41 having primary 42, secondary 43, and balancing coil 44 connected in the same manner as transformer 7. A tuning condenser 45 across secondary 43 is provided to control the output which is fed into a detector and audio amplifier. Obviously any number of radio frequency stages may be inserted between the antenna and detector.

Each radio frequency transformer preferably comprises a primary coil 14 wound on an elongated, here shown as cylindrical, insulating tube 50. Secondary coil 25 is similarly disposed on a tube 51. These two tubes are preferably of different cross-sectional dimensions whereby one may be disposed within the other. As shown, the primary coil is within the secondary and coaxial therewith. In order to rigidly maintain the tubes suitable fastening means such as eyelets 52 are provided at least at one end. Bushings 53 are disposed over the eyelets between the opposing surfaces of tubes 50 and 51 to maintain the spacing and increase the rigidity of the entire structure. shown, inner primary coil tube 50 is shorter than the outer tube and is completely supported thereby. Balancing coil 31 wound on'a tube 55 is disposed at the end of the primary coil with its axis transverse to the axis of the primary and secondary coils. In order to support the balancing coil tube, its ends are cut at an acute angle to the axis to provide tongues 56 abutting the inner surface of tube 50. Small metallic angle pieces 58 are riveted to these tongues and to the end of tube 50 at 60 thereby rigidly maintaining the balancing coil in position.

- The entire transformer structure is mount ed on a metallic base 61 by angle pieces 62 riveted at 60 to tube 51. This base is grounded in practice and has one end of balancing coil 31 connected thereto. The remaining connections are made to suitable terminals. The connecting wires may be threaded through suitable holes in base 61. Base 61 has a peripheral flange 64 and is adapted to have a shield or cap 65 fit tightly around'said flange. The entire transformer structure is thus protected against mechanical shock and electrical disturbance.

It is noted, in this instance, that inner tube 50 terminates near the top of balancing coil 31. It is obvious, however, that the two concentric tubes may be made of equal length and that the balancing coil may be made sufficiently small so that it maybe fastened to the inner tube in substantially the same manner as now fastened to the outer tube.

What I claim is:

1. A balanced radio-frequency transformor comprising primary and secondary coils wound on tubes having different cross-sectional dimensions, means for maintaining said tubes in coaxial relation, a balancing coil wound on a tube, the ends of said last-named tube being cut at an acute angle to its axis whereby tongues are formed, and means for mounting said balancing coil tube by said tongues within one of said other tubes.

2. A balanced radio-frequency transformer comprising a primary and secondary wound on tubes having different cross-sectional dimensions, one of said tubes being within the other, means at oneend of each of said tubes for rigidly maintaining them in coaxial relation, a balancing coil wound on a tube, said last-named tube having its ends cut at an acute angle whereby tongues are formed, and means at the end of one of said tubes for engaging said tongues for maintaining said balancing coil so that its axis is transverse to the axis of the other two cons.

3. A balanced and shielded radio-frequency transformer comprising a base, primary and secondary coils wound on insulating tubes having different cross-sectional dimensions, one of said tubes being within the other and coaxial therewith, means for mounting one of said tubes only at its end on said base, means at the free end of said mounted tube for supporting said other tube therefrom, a balancing coil wound on an insulating tube, means for supporting said balancing coil tube on one of said other tubes and entirely within it so that the balancing coil axis and the axis of the other two coils are perpendicular, and a metal cap engaging the base and covering the entire structure.

4. A balanced and shielded radio-frequency transformer comprising a metal base, primary and secondary coils wound on insulating tubes having different cross-sectional dimensions, the primary being within the secondary and coaxial therewith, means for supporting the secondary on said base at one end thereof, means at the free end of said secondary for supporting said primary, a balancing coil wound on an insulating tube, means for supporting said balancing coil tube at one end of one of said other tubes and entirely within it so that the balancing coil axis is perpendicular to the axis of the other two coils and a metal cap engaging said base and completely covering said transformer.

5. A balanced and shielded radio-frequency transformer comprising a metal base, primary and secondary coils wound on insulating tubes, said tubes having difierent crosssectional dimensions, said primary being within the secondary and coaxial therewith, means at one end of said secondary coil tube for supporting it on said base, means at the other end of the secondary coil tube and engaging an end of the primary coil tube for supporting the latter, a balancing coil wound on an insulating tube, means for supporting said balancing coil tube on said secondary coil tube and entirely within it so that the axis of the balancing coil is perpendicular to the axis of the other coils and a metal cap engaging the base to cover and protect the transformer.

6. A balanced and shielded radio-frequency transformer comprising a metal base, primary and secondary coils wound on insulating tubes having different cross-sectional dimensions, the primary being disposed entirely within the secondary and coaxial therewith, means at one end of said secondary tube for supporting it on said base, means at the other end of said secondary coil tube for supporting the primary coil tube, a balancing coil Wound on an insulating tube, the ends of said tube being cut at an acute angle with the axis thereof thereby forming tongues, means co-operating with said tongues and an end of one of said other tubes for supporting said balancing coil within said secondary whereby the balancing coil axis is perpendicular to the axis of the other coils, and a metal cap engaging said base to al 0 end of said secondary coil tube for supporting the primary coil tube, said primary coil structure.

ap engaging said base and covering said In testimony whereof he aifixes his signature.

tube being shorter in len th than said secondary coil tube, a balancing coil wound on an insulating tube, means for supporting said balancing coil tube entirely within said secondary coil tube only and adjacent said primary coil tube so that the balancing coil axis is perpendicular to the axis of other coils and a metal cap engaging said base and covering said structure.

8. A balanced and shielded radio-frequency transformer comprising a metal base, primary and secondary coils wound on insulating tubes having different cross-sectional dimensions, the primary beirfg within the secondary and coaxial therewith, means at one end of the secondary coil tube for supporting said tube on said base, a plurality of eyelets passing through the free end of said secondary coil tube and an end of the primary coil tube for supporting the latter, a balancing coil wound on an insulating tube, the ends of said balancing coil tube being cut at an acute angle to the axis thereof thereby forming tongues, means for supporting said balancing coil tube within said secondary coil tube only and adjacent the primary coil tube with the axis of the balancing coil perpendicular to the axis of the other two coils, and a metal cap engaging said base and covering the entire structure.

9. A balanced and shielded radio-frequency transformer comprising a metal base, primary and secondary coils wound on insulating tubes having different cross-sectional dimensions, the primary being within the secondary and co-axial therewith, means at one end of the secondary coil tube for supporting said tube on said base, a plurality of eyelets passing through the free end of said secondary coil tube and an end of the primary coil tube for supporting the latter, bushings surrounding each of said eyelets between the opposing tube surfaces to space the latter, a-

balancing coil wound on an insulating tube, v

the ends of said tube being out at an acute angle to the axis thereof thereby forming tongues, means for supporting said balancing coil tube within the end of said secondary coil tube adjacent the base, said balancing c011 being adjacent said primary coil and having its axis perpendicular to the axis of the primary and secondary coils, and a met- RUSSELL H. HAMMALN. 

